1. Field of the Invention
The present invention concerns an x-ray tube of the type having a stationary cathode and a rotating anode in a vacuum housing, the anode being positioned on a housing-fixed axle such that it can be rotated, and the rotating anode being formed as a hollow body with an interior an axle-fixed ring projection is disposed.
2. Description of the Prior Art
X-ray radiation conventionally is generated by bombarding an anode with an electron beam originating from a cathode. The cathode and the anode are arranged in a vacuum housing. The anode typically is a rotating anode that rotates under the incident electron beam in order to prevent the focal spot from being stationary with respect to the anode. The focal spot, meaning the point at which the electron beam strikes the anode surface, moves (when viewed in the context of a coordinate system rotating with the rotating anode) along a circular path over the anode surface. The heat generated by the impact of the electron beam thus is relatively uniformly distributed on the anode surface for countering material overheating in the focal spot.
Bearing requirements for such a rotating anode are significant because the anode is frequently operated with high angular rotation speeds and acceleration rates, and correspondingly high angular acceleration can occur. Additionally, an optimally good heat dissipation from the rotating anode must be ensured in order to prevent overheating of the x-ray tube.
An x-ray tube of the initially cited type is known from European Application 0 328 951. In this known x-ray tube, the rotating anode is rotatably positioned on a housing-fixed axle passing completely through it. The bearing ensues with roller bearings arranged on both sides of the rotating anode in the axial direction. For a good heat removal, the rotating anode is formed as a hollow body in the interior of which an axle-fixed heat absorption body, through which coolant flows, is disposed. The rotating anode and the heat absorption body are separated by a thin gap via which heat is radiated from the rotating anode onto the heat absorption body.
An x-ray tube with a rotating anode driven by a central drive axle is known from United States Patent Application Publication No. 2002/0085676. The drive axle is supported by ball bearings in a tube-like guide. The guide in turn is surrounded by a heat exchanger disposed in the hollow rotating anode such that, between the inner wall of the rotating anode and an adjacent wall of the heat exchanger, a gap is formed that is filled with a fluid heat transfer medium, in particular a liquid metal, for the effecting of a good heat coupling to the rotating anode.
Furthermore, for example from German OS 195 23 162, it is known to use a liquid-metal fluid bearing for the rotating anode of an x-ray tube.